Nitride compound semiconductors are often used in LEDs or laser diodes, which generally emit in the blue spectral range. Depending on the composition of the semiconductor material, emission in the ultraviolet or green spectral range is, for example, also possible. The shortwave radiation may be converted to longer wavelengths through luminescence conversion using luminescent materials. This makes it possible to produce polychromatic light, in particular white light. LEDs based on nitride compound semiconductors are therefore of considerable significance for LED illumination systems.
When producing optoelectronic devices, the nitride compound semiconductor layers are generally grown epitaxially onto a growth substrate which is conformed to the lattice constant and the crystal structure of the nitride compound semiconductor material. Suitable substrate materials are in particular sapphire, GaN or SiC. These substrate materials are comparatively expensive, however.
The growth of nitride compound semiconductors on comparatively inexpensive silicon substrates is complicated by a comparatively large difference in the coefficients of thermal expansion of the silicon and the nitride compound semiconductor material. In particular, cooling of the layer system from the growth temperature of around 1000° C. used to grow nitride compound semiconductors to room temperature creates major tensile strains in the GaN.
German Patent document DE 10 2006 008 929 A1 and International Patent Publication WO 2011/039181 A1, also published as counterpart U.S. Pat. No. 8,828,768 B2, each describe methods for producing nitride compound semiconductor devices on silicon substrates. It is known from these documents to incorporate between the silicon surface of the growth substrate and the functional layer sequence of the optoelectronic device a layer structure for producing a compressive strain, which counteracts the tensile strain produced by the silicon during cooling.
International Patent Publication WO 2013/045355 A1, also published as counterpart U.S. Publication No. 2014/0302665 A1, describes a method for producing nitride compound semiconductor devices on silicon substrates in which a layer structure is arranged between the silicon substrate and the functional layer sequence of the optoelectronic device, wherein a masking layer of a silicon nitride-containing material is embedded in the layer structure. By embedding the masking layer a reduction in dislocation density is achieved. However, embedding a layer of a material such as, for example, silicon nitride which does not belong to the material system of the other semiconductor layers is associated with increased manufacturing effort.